Materials research: Qi-ya, physics.

http://arxiv.org/abs/1305.3760

Really really interesting physics article on Qi-yi, which is the tendency of chinese scrolls to curve outwards across their length.

IF i am reading this correctly (and it is possible that I am not, becuase my knowledge of physics is extremely limited), it suggests that this tendency comes from the way these scrolls are stored rather than the way they are mounted.

it suggests a few ways to mitigate this:
1) "align the main fiber direction of backing paper... along the length."
2) add extra layers to the side borders
3) poke the backside of the scroll with a stiff brush-- already a practice in japanese mounting, poke not in region 1 (not entirely sure where that is-- i think it's the actual region which curves, so the outter edges???). japanese practice pokes the entire paper.
4) use a larger roller for storage than for display.

Further research which may be useful:

How to mount paintings on paper and on cloth
japanese scroll techniques
japanese scroll mounting techniques
chinese scroll mounting techniques
how to size paper
how to size cloth